The present invention relates to a lattice girder for tunnel construction.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Arches that are formed during tunnel advancement must be supported with the aid of support trusses that are shaped to suit the excavation geometry. During subsequent lining with shotcrete, the individual support trusses are surrounded by concrete. The use of metallic lattice girders as frameworks has proven useful as opposed to the use of solid profiles for the support truss. Lattice girders save material and weight while exhibiting no unconsolidated areas or voids as opposed to solid wall profiles which encounter spray shadows. The individual lattice girders are assembled on site to form juxtaposed lattice arches in circumferential direction of the excavation. The shotcrete lining is homogenous due to the open structure of the lattice arch. The various lattice girders provide high bonding quality with the shotcrete lining and reliable level of support in tunneling.
It would be desirable and advantageous to provide an improved lattice girder which obviates prior art shortcomings and which can be constructed for simple connection with further lattice girders so as to enable easy storage, transport and stacking capability of several lattice girders.